the fbi. that and tonight's monthly making a difference report. nightly ne "nbc nightly news" begins you now. >>> it appears we came very close to having to come on the air with a special report about the latest mass casualty disaster on a major college campus. this time it was on the sprawling campus of the university of central florida in orlando. police say a student was heavily armed with homemade explosives and an assault weapon. they say he had a plan of attack which he had initiated, but thankfully apparently someone saw something and said something, and tonight a huge tragedy has apparently been averted. nbc's mark potter starts us off from there tonight. >> it was shortly after midnight when the tara i dorm after midnight was evacuated. police received a 911 call followed by a student who was hiding in a bathroom after the roommate pulled a gun on him.